This invention relates to an emulsifier system for liquid or powder nutritional products.
In addition to its essential role in nutrition, protein is an important contributor to the physical properties of formulated foods including infant formulas and foods formulated for special medical purposes. Intact proteins and partially hydrolyzed proteins contribute to the emulsification of a fat component of a nutritional product due to their favorable hydrophilic-lipophilic balance that facilitates adsorption at the interface during preparation of product. Intact proteins and partially hydrolyzed proteins also contribute to forming a strong and cohesive interfacial film that minimizes droplet coalescence in the product resulting in a stable emulsion which allows manufacture of liquid and powder nutritional products with acceptable physical properties and shelf-life.
Foods containing extensively hydrolyzed protein and/or free amino acids are frequently referred to as elemental diet products. Elemental diets contain the altered protein components to fit with special medical purposes for a selected population with suspected protein allergy, protein intolerance, malabsorption disorders, or inborn errors of metabolism. Hypoallergenic infant formulas represent an important diet alternative for babies with demonstrated protein allergy to cow""s milk. In contrast to intact protein or partially hydrolyzed protein, extensively hydrolyzed protein and amino acids have very poor or negligible emulsifying properties. In the products utilizing extensively hydrolyzed protein and/or free amino acids, commercially available emulsifiers have been used to achieve acceptable physical characteristics. One such emulsifier frequently used in infant formulas and other formulated nutritional products having extensively hydrolyzed or free amino acids is an octenyl succinic anhydride modified starch (hereinafter xe2x80x9cOSA modified starchxe2x80x9d). It is believed that the modification of the starch contributes to emulsion stability of the formulation by reducing the boundary tension between the immiscible fluids oil and water. The OSA starch is available commercially as intact (no molecular weight reduction) or dextrinized (molecular weight reduced by heat or enzymatic treatment and the like).
When proteins, hydrolyzed proteins and/or amino acids and carbohydrates are combined in an aqueous solution, these components have a tendency, especially with time and at elevated temperatures, to form a brownish solution and undesirable by-products due to the well-known Maillard reaction(s). This problem is particularly challenging for formulas prepared with extensively hydrolyzed proteins and/or free amino acids. U.S. Pat. No. 4,414,238 (Schmidl) teaches an elemental diet composition that uses an OSA modified starch in combination with a mono- and diglycerides emulsifier at a pH range of from about 3 to 4.4 to provide acceptable emulsification stability in conjunction to reduce the Maillard reaction. The pH range is attributed to providing an aqueous combination that is non-browning with time and at elevated temperatures and can be pasteurized or sterilized without the formation of Maillard reaction related by-products or undesirable browning.
U.S. Pat. No. 4,670,268 (Mahmoud) teaches that an OSA modified starch may be used in formulations with extensively hydrolyzed proteins at a higher pH of from 6 to 7. This patent also teaches that mono- and diglycerides, lecithin and polyglycerol esters of fatty acids were found to be ineffective in producing a stable hypoallergenic formula. As provided in Col. 4, lines 13-16 of U.S. Pat. No. 4,670,268, the hypoallergenic formula made with these emulsifiers yielded unstable emulsions and developed an objectionable cream layer within 24 hours of sterilization.
The OSA modified starch has been found incompatible with simple emulsifiers, as discussed in the prior art literature and exemplified in the Examples section herein. Thus, in commercially available nutritional products with extensively hydrolyzed proteins, dextrinized OSA modified starch is often used as asole emulsifier in elemental diet compositions (see, e.g., U.S. Pat. No. 4,670,268).
While products with extensively hydrolyzed proteins and/or amino acids are commercially available, alternative emulsifying systems for elemental diets are needed.
An alternative emulsifying system for elemental diet compositions has been discovered. The inventive elemental diet composition comprises (a) a protein source selected from the group consisting of extensively hydrolyzed protein, free amino acids, short-chain peptides, or a mixture thereof; (b) a lipid source; (c) a carbohydrate source; and (d) an emulsifying system comprising OSA modified starch and an acetylated monoglyceride emulsifier.
The inventive composition may be prepared as a powder or liquid nutritional composition for formulas prepared for infant, pediatric and adult populations in need of an elemental diet. The inventive composition may be prepared as a nutritionally complete diet by including vitamins and minerals at acceptable levels. The invention provides a commercially acceptable product in terms of desired stability and physical characteristics and the product demonstrates little to no observable browning effect by-products associated with a Maillard reaction. Further, the inventive composition is substantially homogeneous for an acceptable period after reconstitution (or for the shelf-life if prepared as a liquid). The invention is particularly useful for hypoallergenic infant formula preparations, although it is equally applicable to other elemental diets specific to a selected population with suspected protein intolerance, malabsorption disorders, inborn errors of metabolism, and the like.
The protein source may be selected from any appropriate nitrogen sources, such as, extensively hydrolyzed protein, free amino acids, short-chain peptides and mixtures thereof appropriate for formulation of elemental diet compositions targeted for populations having specific nutritional needs. The actual amino acid/ peptide content will depend upon the desired nutritional goals of the particular composition. Favored proteins include extensively hydrolyzed protein hydrolysates prepared from acid or enzyme treated animal and vegetable proteins, such as, casein hydrolysate, whey hydrolysate, casein/whey hydrolysate, soy hydrolysate, and mixtures thereof. By xe2x80x9cextensively hydrolyzedxe2x80x9d protein hydrolysates it is meant that the intact protein is hydrolyzed into peptide fragments whereby a majority of peptides fragments have a molecular weight of less than 1000 Daltons. More preferably, from at least about 75% (preferably at least about 95%) of the peptide fragments have a molecular weight of less than about 1000 Daltons. Free amino acids and synthetic short peptide chains may also be either substituted for or added to the protein hydrolysates as the nitrogen source so long as the nutritional composition has an amino acid profile suitable for the targeted population, as within the skill of one familiar with the art of nutritional formulations.
The amount of protein employed in the nutritional composition may be determined by the nutrient profile targeted for a specific formulation, as well known to those skilled in the art. For example, for infant formulas, the protein source typically comprises approximately from about 8 to about 20 percent of total calories, more preferably from 10 to 12 percent of the total calories of the nutritional composition.
The lipid or fat source may be any FDA approved natural and/or synthetic oil that is edible and acceptable for use in elemental diet compositions, employed in an amount suitable for the desired nutritional balance for the specific formulation, as known to those skilled in the art. For example, for infant formulas, the fat source will contribute from about 35 to about 55 percent of total calories, more preferably from 40 to 50 percent of total calories of the nutritional composition. Nutritional formulas generally employ linoleic acid in amounts ranging from about 2.7 to about 10 percent of the total calories of the formula to meet typical nutritional goals, particularly if the formula is nutritionally complete. Suitable fat sources include medium chain triglycerides (MCT), synthetic and vegetable oils, including but not limited to palm olein, soy, coconut, and high oleic sunflower oils and the like, as well known in the art. The acetylated monoglycerides emulsifier used in accordance with this invention may be factored into the total fat content of the overall composition on a w/w basis, as discussed in more detail hereinafter.
The carbohydrate source may be selected from any FDA approved natural and/or synthetic carbohydrates, including by way of example, maltodextrin, polydextrose, dextrose, sucrose, lactose, mixtures thereof, and so on. The carbohydrate component may be added in amounts desired in the nutrient profile of the final composition. For example, the carbohydrate may be contribute anywhere from about 35 percent to about 70 percent of total calories, preferably from 40 to 50 percent for infant formulas. Additionally, the OSA modified starch that is part of the emulsifier system of the invention contributes to the carbohydrate content of the final formulation and may be included in the total carbohydrate.
In one preferred embodiment, glucose polymers comprise the primary source of carbohydrate. In this preferred embodiment, glucose polymers are favored because of their formulation properties and because they are considered more easily digested and tolerated by infants whose capacity to handle lactose and sucrose may be impaired. The preferred glucose polymers are prepared utilizing filtration and purification procedures which remove virtually all traces of protein. Preferably at least about 50%, more preferably at least about 70% of the total carbohydrate is comprised of glucose polymers having a degree of polymerization of from 3 to 7, and a preferred average of four glucose units. Based on cost and availability, the preferred glucose polymers are used in the form of corn syrup solids, although the syrup may also be prepared from rice, sorghum, tapioca, barley, and the like. Particularly useful as a carbohydrate source are corn syrup solids having a degree of polymerization of about an average of four glucose or and a dextrose equivalents (DE) of about 24. For the preferred embodiment, the selection of the carbohydrate source is believed to assist in preparing a final formulation that substantially avoids observable browning attributed to a Maillard reaction without requiring that the formula be highly acidic.
The inventive composition may be prepared having a pH level acceptable to the targeted specification of the elemental diet, so long as the Maillard reaction by-products are avoided to the point of preparing a commercially acceptable product. It has been found that in a preferred embodiment, the final formula may be prepared to have a pH level of from about 5 to about 6. The pH level of between about 5 and 6 is advantageous as highly acidic formulations are inappropriate for infant formula compositions. Specifically, it has been found particularly advantageous to adjust the pH to a value less than 6 but greater than 5, and most preferably at a value of approximately 5.5 in some formulations.
In addition to the essential protein, lipid and carbohydrate content, the nutritional compositions may include other ingredients such as, for example, vitamins, minerals, non-essential amino acids, pH modifiers (such as citric acid or potassium hydroxide), stabilizers (such as carageenan), fiber, functional ingredients, and the like, in a manner well known to those skilled in the art to achieve the desired nutritional goal of the element diet composition.
Unexpectedly, it is has been found that acetylated monoglyceride emulsifiers are compatible with an OSA modified starch emulsifier and provide an effective emulsifier system for elemental diets. Edible acetylated monoglycerides are widely available commercially, including by way of example, CETODAN(copyright) 90-50 (Danisco Ingredients, New Century, Kans. 66031); and MYVACET(copyright) 9-08 and MYVACET 9-45 (Eastman Chemical Company, Kingsport, Tenn. 37662). Combinations of the commercially available acetylated monoglycerides may also be employed. Preferably the acetylated monoglycerides have a degree of acetylation from about 90 to about 100% and an iodine value from about 2 to about 5. Acetylated monoglycerides are within the lipid category, and thus the amount of lipid in the formulation should be reduced or offset according to the amount of added acetylated monoglyceride(s), as within the capabilities of those skilled in the art.
Because it has been found that the intact OSA modified starch has been found to be more rugged in terms of stability (as compared to dextrinized OSA modified starch), intact OSA starch is more desirable for some applications. Intact OSA modified starch is widely available commercially, as prepared for example, by esterifying a waxy grain (corn, rice, tapioca, etc.) starch with 1-ocetnyl succinic anhydride. Commercially available dextrinized and intact OSA modified starches are prepared by esterifying of a waxy corn starch with octenyl succinic anhydride are particularly well-suited for the present use and include, by way of example, E-Z FILL (Cerestar USA Inc., Hammond, Ind. 46320); NATIONAL 6912 (National Starch and Chemical Corporation, Bridgewater, N.J. 08807), and STALEY 365 (A.E. Staley Manufacturing Company, Decatur, Ill. 62525).
The OSA modified starch and acetylated monoglyceride emulsifier system is added to the formulation in an amount effective to provide a commercially acceptable stable formulation. The amount may be determined based on the emulsification needs of the formulation. For example, combinations of from about 0.1 about 10 weight percent OSA modified starch and from about 0.01 to about 7.5 acetylated monoglyceride emulsifier may be employed. As used herein, weight percentages of the OSA modified starch and acetylated monoglyceride emulsifier are based on the total weight of the inventive composition prepared in a ready to feed form (i.e., powder form is reconstituted or liquid concentrate is diluted by the addition of water). An ideal combination of emulsifiers comprises from about 0.5 to about 2 weight percent OSA modified starch and from about 0.04 to about 0.1 weight percent acetylated monoglyceride emulsifier.
A liquid elemental diet product is often more challenging to formulate as compared to formulating a powder product because the liquid product ingredients must be suspended in a commercially acceptable uniform manner over the shelf-life of the liquid product. It has been found that more OSA starch may be required when formulating liquid products compared to powder products. For liquid products, preferably from about 1 to about 1.7 (more preferably 1.6 to 1.7) weight percent OSA modified starch is used. For powder products, preferably from about 0.7 to about 1.5 (more preferably 0.9 to 1.1) weight percent OSA modified starch is used. The preferred amount of acetylated monoglyceride employed in the emulsifier system may range from 0.04 to about 0.1 weight (most preferably, from about 0.05 to about 0.07 weight percent) for either powder or liquids. The more preferred ratio of OSA modified starch:acetylated monoglyceride is from about 85 to about 97 parts OSA modified starch to 3 to 15 parts acetylated monoglycerides, most preferably for liquids about 96 parts OSA modified starch to about 4 parts acetylated monoglyceride.
The compositions of the invention exhibit desired stability as measured by a number of known tests used within the nutritional industry. Criteria for evaluating the stability include measurements of average fat globule diameter prior to and following sterilization and/or freeze thaw treatment as shown in the Example section hereinafter. Further, to meet the demands of a commercial product, the compositions may be evaluated in terms of physical properties, including the appearance of products in quiescent storage, in particular, creaming, free oil, and serum formation (i.e., product homogeneity).